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Edited by Tom Kuhar, Assistant Professor, Dept. of Entomology, Virginia Tech
Greetings crop producers, researchers, extension personnel, and crop consultants.
Blacklight and Pheromone Insect Traps
Jack Speese & Tom Kuhar (ESAREC)
Weekly catch:
Blacklight trap (BLT) in Painter, VA: 2 European corn borer moths, 3 true armyworm moths, 23 green stink bugs, 352 brown stink bugs, 20 tobacco wireworm click beetles
BLT in Cheriton, VA: 15 ECB moths, 1 variegated cutworm moth, 11 corn earworm moths, 2 true armyworm moths, 2 beet armyworm moths, 1 green stink bug, 62 brown stink bugs, 10 tobacco wireworm click beetles
Due in part to heavy thunder shower activity, we're not catching very many of the agricultural pest moths at this time, although in Cheriton we detected some beet armyworm moth activity and a few corn earworm moths. Low numbers of European corn borer moths were caught at both sites. Brown stinkbug adult activity is picking up, especially at Painter. This pest can damage fruiting vegetables by feeding on buds and fruit. Tobacco wireworm click beetles are flying; peak flights of this pest occur in July and then diminish rapidly in August. These beetles lay eggs in sweetpotatoes and fall potatoes. The eggs hatch into the next generation of wireworms in time to cause late season damage in these crops.
Northampton County news from our roving reporter in the field
(Bill Shockley (VCE, Northampton Co.)
We're seeing some heavy thrips pressure in soybeans. European corn borers are being found in pods of some recently harvested green beans.
Continued thrips activity on crops
Jack Speese and Tom Kuhar (ESAREC)
This year we have observed heavy thrips pressure in several crops in Virginia, namely cotton, tomatoes, and now soybeans. Thrips are tiny, narrow-bodied insects, and the species that commonly feeds on soybeans is alternately dark and light banded. Thrips larvae resemble the adults, but are yellow in color, smaller, and wingless. The presence of larvae indicates that the thrips are well-established and reproducing the host plant. Thrips can be seen by careful inspection with the naked eye, and a hand lens helps. One can also readily detect thrips by shaking the leaves of an infested plant over a light-colored card, against the background of which the darker-colored, actively moving bodies of the thrips are readily visible. Soybean foliage fed upon by thrips appears streaked and has yellowish discolorations, and severe feeding will cause the new leaves to appear wrinkled or cupped.
Soybeans are able to tolerate thrips in most years, however, they may be injured by heavy thrips pressure when they are small, especially under drought stress. If the plants are under drought stress and more than eight thrips larvae and/or adults per leaflet are observed, treatment is recommended. Lannate, Penncap-M, and Warrior are recommended for thrips control in Virginia. See the Commercial Production Guide for more details, and be sure to follow all label directions.
Thoughts on European corn borer and Bt corn in VA
Rod Youngman (Dept. Entomology, Virginia Tech)
The following are some of my thoughts on the extent of European corn borer pest status in Virginia, and what my/Extension's position should be for the rest of the '04 growing season and for next year. By way of review, we all know the main problem for the '03 growing season was the unprecidented amount of late-planted corn due to the almost non-stop rainfall. My previous field trials with Dan Brann quickly showed what every eastern Virginia corn farmer already knew about late-planted corn, i.e., "Corn borer'll eat it up." Subsequently, for the past 5-6 years my recommendation for late-planted cornfields has been to plant Bt hybrids.
As for the '04 season, I've gotten more calls than usual about ECB infested cornfields. Reports have indicated that ECB damage ranges from light to moderate infestations to fields that will likely suffer reduced grain yields at harvest.
Selected examples include:
Paul Davis reported for his two counties one severely infested field, with only a few instances of lesser damaged fields.
For Essex Co., Keith Balderson reported an increase in cornfields with moderate damage (but probably not economic), along with a scattering of fields exhibiting heavier damage that probably will result in economic grain yield losses.
Wes Alexander and Bobby Clark have reported similar results as Keith for their county/region, respectively.
It's pretty clear that we're experiencing an above normal number of ECB infested cornfields across the state this year, but it has not culminated in a region-wide outbreak for any part of the state. The real issue is what this means for the second generation ECB flight and egg laying activity. Clearly, all non-Bt cornfields should be scouted this year for second-generation egg masses and treated accordingly if warranted. Unfortunately, few farmers in Virginia have the capability to treat for second-generation corn borers because corn plant height by mid-July usually restricts field access to all but aerial applications.
As you know, our historic inability to predict before planting whether a cornfield will experience economic loss from ECB leaves us all in a difficult position. My position for next year essentially is the same I've had for some time, and that is to tell farmers who have heightened concerns about ECB for next year to consider planting Bt corn hybrids in those fields they think are at greatest risk. In addition, with the 20% non-Bt corn acreage they must plant to be in compliance with the resistant management requirement, they'll be able to make their own side-by-side comparisons on how much, if any, the Bt corn they planted has benefited over the non-Bt corn.
Cotton insect update
Ames Herbert (Tidewater AREC)
THRIPS: Thrips were tough this year with very high populations in our untreated cotton controls (in our several field tests) with peaks of 40-50 immatures and 10-20 adults per seedling. However, a variety of control products have worked very well and held. By now, we are on the other side of the thrips problem and getting geared up for the next set of insect issues: aphids, mites and the bug species (plant bug/stinkbug complex).
APHIDS, SPIDER MITES: No treatable levels of either aphids or spider mites have been reported, although you can find them in low numbers in a lot of fields. We are seeing good predator and parasite activity and if we continue to get timely rains, we should escape those problems, at least for now.
PLANT BUGS/STINKBUGS: We are just getting started with our field experiments and surveys for bug species. We are doing sweep net and ground cloth sampling for the insects and doing square retention counts on several growers' fields. Cotton fields are squaring with anywhere from 3-4 to 10-15 squares per plant, depending on the growers' variety, planting date, etc. No blooms as yet. We are finding tarnished plant bug in every field if you search hard enough, but no stinkbugs as yet. Only one out of the several we are surveying has a potentially dangerously low square retention rate (86%). Most are above 99 percent. Below are a few comments by Dr. Jack Bacheler at NC State regarding plant bugs and control.
Plant bugs are not an economic problem on pre-blooming cotton if the retention of small squares is 80 percent or greater. Monitoring the retention rates of small squares is the easiest way to keep abreast of potential plant bug problems in pre-blooming cotton. If the square retention rate drops below 80 percent, then sweeping with a standard net is recommended. The finding of small, blackened squares is often an indication of recent of plant bug activity. Sets of 25 rigorous sweeps down and through cotton rows in 8 to 10 randomly-selected areas in a cotton field should provide some idea if treatable levels of plant bugs are present. Observe cotton field edges for indications of plant bug migration and the possible need for shorter monitoring intervals, but do not oversample these areas. In North Carolina, we typically treat only about 5 to 8 percent of our cotton fields for plant bugs at this time of year, though plant bugs can cause heavy damage, particularly in some of our far eastern counties. Weekly assessments of square retention should be regarded as the minimal monitoring approach for the initial detection of potential plant bug damage. Dr. Jack Bacheler, NC State
BOLLWORM: We are just beginning to catch our first bollworm (corn earworm) moths in our blacklight and pheromone traps. Numbers are very low - but they always start that way.
We have a lot planned for this season including a weekly insect advisory beginning soon, vial testing bollworm moths for pyrethroid resistance, bug species surveys and tests, and much more.
Two new insecticides registered for cotton, soybean, peanut, wheat and many other commodities.
Ames Herbert (Tidewater AREC)
Dow AgroSciences has just gained registration for two new insecticides, Proaxis and Prolex, for use in several commodities. They both have the same active ingredient, gamma-cyhalothrin, which is a pyrethroid and chemically similar to lambda-cyhalothrin, the active ingredient in Karate and Warrior.
Prolex is like Karate, as it has the high concentration (1.25 lb ai/gallon), and Proaxis is like Warrior with the lower concentration (0.5 lb ai/gallon).
Prolex is labeled for cotton, peanut, soybean, sorghum (grain), rice, sugarcane and non-crop areas adjacent to crops.
Proaxis is labeled for cotton, peanut, soybean, wheat as well as many other fruits, vegetables, nut trees and others.
We have done some field trials with this active ingredient in past years and would expect good control of those pests where pyrethroids do a good job. We are planning more field tests this season. Please consult the labels for suggested rates and other legal constraints and regulations regarding these new products.
Thomas P. Kuhar
Assistant Professor
Department of Entomology
Eastern Shore Agricultural Research & Extension Center
Virginia Polytechnic Institute & State University
33446 Research Drive
Painter, VA 23420
E-mail: tkuhar@vt.edu
Tel: 757-414-0724
FAX: 757-414-0730
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